Cancer therapies comprise a wide range of therapeutic approaches, including surgery, radiation, and chemotherapy. While the often complementary approaches allow a broad selection to be available to the medical practitioner to treat the cancer, existing therapeutics suffer from a number of disadvantages, such as a lack of selectivity of targeting cancer cells over normal, healthy cells, and the development of resistance by the cancer to the treatment.
Recent approaches based on targeted therapeutics, which interfere with cellular processes of cancer cells preferentially over normal cells, have led to chemotherapeutic regimens with fewer side effects as compared to non-targeted therapies such as radiation treatment. Nevertheless, cancers treated with targeted therapeutics may still develop resistance. For example, resistance to bevacizumab, a monoclonal antibody therapeutic that targets VEGF-positive cancer cells, has been reported in some colorectal cancers (Mesange et al. Oncotarget 2014; 5(13): 4709-4721).
A mechanism for treatment resistance is believed to be the formation by activated fibroblasts (e.g., cancer associated fibroblasts (CAFs), mesenchymal stem cells (MSCs)) in the tumor microenvironment which prevents cancer drugs from physically reaching the cancer cells (Kalluri R., Nature Reviews Cancer 2016; 16: 582-598). In addition, the fibroblast-mediated stromal barrier is understood to give rise to an immunosuppressive environment that can prevent immune effector cells from penetrating deep into the tumor and targeting cancer cells (Turley, S. J. Nature Reviews Immunology 2015; 15:669-682). Hence, a cancer drug that targets these stromal fibroblast populations within the tumor microenvironment would complement existing therapeutic strategies and may overcome chemoresistance and increase sensitivity to immune mediated therapies.
Another source of treatment resistance is thought to be the plasticity of cancer cells. For example, the plasticity of cancer cells between epithelial and mesenchymal states has been implicated as a mechanism for the generation of cancer stem cells, which can initiate tumors, as well as serve as a starting point for metastasis. See Ye, X.; Weinberg, R. A. Trends in Cell Biology 2015; 25 (11): 675-686. Further, mesenchymal cancer cells have been reported to be resistant to standard cancer therapies, such as docetaxel. See Singh and Settleman. Oncogene 2010; 29(34): 4741-4751; Ippolito, L. et al. Oncotarget 2016; 7 (38): 61890-61904. A cancer therapy that is effective against these resistant cancer cells would complement existing therapeutic approaches.
Thus, cancer therapeutics that spare normal cells and are less prone to developing clinical resistance would provide additional options for treating cancer, such as by augmenting existing standard of care regimens.